EP0079658B1 - Système de transmission à modulation par impulsions codées différentielles - Google Patents

Système de transmission à modulation par impulsions codées différentielles Download PDF

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Publication number
EP0079658B1
EP0079658B1 EP82201438A EP82201438A EP0079658B1 EP 0079658 B1 EP0079658 B1 EP 0079658B1 EP 82201438 A EP82201438 A EP 82201438A EP 82201438 A EP82201438 A EP 82201438A EP 0079658 B1 EP0079658 B1 EP 0079658B1
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Prior art keywords
signal
prediction
input
circuit
dpcm
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EP82201438A
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German (de)
English (en)
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EP0079658A1 (fr
Inventor
Joseph Hubertus Peters
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Koninklijke Philips NV
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Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00—Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • H03M7/30—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
    • H03M7/3002—Conversion to or from differential modulation
    • H03M7/3044—Conversion to or from differential modulation with several bits only, i.e. the difference between successive samples being coded by more than one bit, e.g. differential pulse code modulation [DPCM]

Definitions

  • the invention relates to a transmission system comprising a transmitter and a receiver, for transmitting an information signal, a video signal in particular, in a digital format obtained by means of differential pulse code modulation (DPCM).
  • the transmitter of this system comprises a DPCM-encoding arrangement and the receiver a DPCM-decoding arrangement.
  • the transmitter of a transmission system generally comprises a source supplying an information signal in the analog or digital form and which must be transmitted to the associated receiver.
  • this information signal is first applied to a source encoding circuit which here is in the focm of a DPCM-coding arrangement.
  • a source encoding circuit which here is in the focm of a DPCM-coding arrangement.
  • such coding arrangement comprises a difference producer to which the information signal and a prediction signal are applied and produces a difference signal.
  • This difference signal is applied to a quantizing arrangement producing a quantized difference signal.
  • the DPCM-encoding arrangement comprises a prediction circuit having an input and an output. The quantized difference signal is applied to the input of this prediction circuit and the said prediction signal occurs at its output.
  • the quantized difference signal occurring at the output of the quantizing arrangement is further applied to a channel encoding circuit, for example an analog-to-digital converter or a code converter, which converts this quantized difference signal into a digital channel signal which will be denoted DPCM signal hereinafter and consists of a sequence of code words occurring at a predetermined rate f s , denoted the sampling frequency.
  • a channel encoding circuit for example an analog-to-digital converter or a code converter, which converts this quantized difference signal into a digital channel signal which will be denoted DPCM signal hereinafter and consists of a sequence of code words occurring at a predetermined rate f s , denoted the sampling frequency.
  • DPCM signal digital channel signal
  • the inverse quantity 1/f s will be denoted the sampling period and will be indicated by the symbol T.
  • the code words produced by the channel coding circuit are transmitted to the associated receiver, where the sequence of received code words are converted in a channel decoding circuit into a decoded channel signal which, the transmission not being disturbed, accurately corresponds to the original quantized difference signal.
  • This decoded channel signal is further applied to a DPCM-decoding arrangement.
  • a DPCM-decoding arrangement comprises a summing device to which the decoded channel signal and a second prediction signal are applied and which produces a sum signal.
  • This DPCM-decoding arrangement further comprises a second prediction circuit having an input and an output. The decoded channel signal being applied to this input and the second prediction signal occurring at this output.
  • the prediction circuit in the transmitter is of the same construction as the prediction circuit in the receiver, in order to achieve that the sum signal accurately corresponds to the original information signal.
  • a prediction circuit can be implemented in several different ways. Possible implementations are described in, for example, the References 1, 2, 3, 4, 5 and 6. As will be apparent from these References, such a prediction circuit is generally formed by an integrator circuit the input of which is connected to the input of the prediction circuit and the output to the output of the prediction circuit.
  • every received code word now contributes during a predetermined time interval to the sum signal. If now a code word is disturbed in the transmission medium, then also the sum signal is disturbed during an equally long time interval. This time interval is closely related to the time constant of the integrator circuit. If it has an infinitely long time constant (in that case the integrator circuit is sometimes called an ideal integrator circuit) then, after the occurrence of a transmission error the sum signal will never obtain its proper value again. In such a case it is customary periodically to adjust the prediction circuit of the DPCM-coding and decoding arrangement (for example at the end of every TV-line) to a fixed value.
  • the time constant of the integrator circuit is chosen shorter (in that case the integrator circuit is sometimes called a leaky integrator circuit), also the said time interval becomes shorter. However, reducing the time constant results in a decrease of TV-picture quality. The highest picture quality is obtained when an ideal integrator circuit is used. If, however, a leaky integrator circuit is used, the leak factor will always be a compromise between the length of the said time interval (that is to say the speed with which a transmission error is eliminated) and the loss in picture quality.
  • references 7, 8 and 9 propose to add in the transmitter an error reduction signal to the DPCM-signal.
  • This error reduction signal is then generated by an error reduction circuit to which the information signal to be transmitted, or the prediction signal is applied.
  • an error reduction signal is subtracted from the received sum signal in order to generate the original DPCM-signal.
  • this error reduction signal generated in the receiver is produced by an error reduction circuit to which a signal generated in the DPCM-decoding arrangement is applied, and which, when the transmission being undisturbed, corresponds to the best possible extent to the error reduction signal generated in the transmitter.
  • Both the DPCM-encoding arrangement in the transmitter and the DPCM-decoding arrangement in the receiver comprises a prediction circuit which is constituted by a recursive discrete time filter which is formed by a first non-recursive discrete time filter whose output signal is summed to its input signal.
  • This recursive discrete time filter receives as an input signal the output samples of the quantizer arrangement.
  • These prediction circuits each also include a correction channel which is constituted by a non-recursive discrete time filter having also applied thereto the output samples of the quantizer arrangement. It produces an output signal which is summed to the output signal of the first non-recursive discrete time filter.
  • the invention has for its object to shorten considerably in a DPCM-transmission system using prediction circuits each including a leaky integrator circuit the above-mentioned time interval during which a disturbed code word negatively affects the sum signal, without a deterioration of the picture quality.
  • both the prediction circuit in the DPCM-coding arrangement and the prediction circuit in the DPCM-decoding arrangement include two or more congruent prediction channels each consisting of a non-linear network having a non-linear transfer function followed by a leaky integrator circuit, the input of each non-linear network being connected to the input of the prediction circuit, all the integrator circuits being of the same construction, a unique set of weighting factors being associated with each integrator circuit, the outputs of these integrator circuits being connected to inputs of an adder arrangement the output of which is connected to the output of the prediction circuit.
  • DPCM-coding and decoding arrangements can be implemented in different ways, the following description will be limited to the digital implementation.
  • Fig. 1 shows an embodiment of a transmitter of the prior art DPCM-transmission system.
  • This transmitter comprises a TV camera 1 with incorporated video amplifier 2 producing an analog video signal x(t).
  • This video signal is applied to an analog-to-digital converter 3, which produces the digital video signal x(n).
  • This analog-to-digital converter 3 is controlled by sampling pulses occurring with a period T.
  • This digital video signal x(n) now represents the information signal to be transmitted to an associated receiver. For an optimum use of the capacity of the transmission medium, this information is subjected to a source encoding operation.
  • This difference signal is applied to a quantizing arrangement 6 which, as is customary, has a non-linear quantizing characteristic and converts this difference signal into a quantized difference signal d(n).
  • This quantized difference signal d(n) is applied to a prediction circuit 7, which has an input 701 and an output 702 and produces the prediction signal y(n).
  • the quantized difference signal d(n) is subjected to a channel encoding operation and for that purpose is applied to a channel encoding circuit 8, which produces the desired DPCM-signal or channel signal c(n) which is transmitted to the receiver.
  • the receiver shown in Fig. 2 comprises a channel encoding circuit 9 to which the received version c'(n) of the digital channel signal c(n) is applied.
  • This channel decoding circuit 9 operates in a manner which is the opposite of the operation of the channel encoding circuit 8 and it produces the decoded channel signal d'(n), which corresponds to the quantized difference signal d(n).
  • This signal d'(n) is now further applied to a DPCM-decoding device 10, which comprises a summing device 11 to which the signal d'(n) as well as a prediction signal y'(n) are applied for generating a sum signal x'(n) which corresponds to the original digital information signal x(n).
  • the prediction signal y'(n) corresponds to the prediction signal y(n) and is derived from the signal d'(n) by means of a prediction circuit.
  • the prediction circuit in the receiver is perfectly identical to the prediction circuit 7 in the transmitter, the prediction circuit in the receiver is also denoted by the reference numeral 7.
  • the sum signal x'(n) is applied to a digital-to-analog converter 12, whose output is connected to the input of a low-pass filter 13 producing the analog video signal x'(t), which corresponds to the analog video signal x(t), and which is applied to a display tube 15 via a video amplifier 14.
  • a group of weighting factors a(i, k) is associated with the circuit 700(i) shown in Fig. 3. This means that a weighting factor a(i, k) is associated with the constant factor multiplier 705(i, k), as a result of which the output signal of the delay device 704(i, k) is multiplied by the constant weighting factor a(i, k).
  • a weighting factor is equal to or greater than zero and equal to or less than one.
  • an ideal integrator circuit is obtained if the mathematical sum of all the weighting factors associated with the system is equal to unity. If this sum is less than one, a what is commonly referred to as a leaky integrator circuit is obtained.
  • the delay device 704(i, k) has a time delay which will be designated T (k).
  • T (k) a time delay which will be designated T (k).
  • H represents a line period.
  • the prediction circuit 7 comprises only one integrator circuit, for example of the type shown in Fig. 3, so that the input 701 (i) and the output 702(i), respectively, of this integrator circuit is connected to the input 701 and to the output 702, respectively, of the prediction circuit 7.
  • the prior art DPCM-transmission system implemented in this way, let the following be assumed.
  • the disadvantageous properties, described in the preceding paragraph of the prior art DPCM-transmission system can be eliminated to a very great extent by assembling the prediction circuit in the manner shown in a general way in Fig. 7.
  • the non-linear network 711(i) is connected by means of its input to the input 701 of the prediction circuit and thus receives the signal d(n) or d'(n) and produces the signal b(i; n) and b'(i; n), respectively.
  • the last-mentioned signal is applied to the integrator circuit 700(i), which in response to the signal b(i, n) produces the auxiliary prediction signal y(i; n) and in response to the signal b'(i; n) produces the auxiliary prediction signal y'(i; n).
  • the auxiliary prediction signals are added together, resulting in the prediction signal y(n) and y'(n), respectively.
  • All the leaky integrator circuits 700(i) are of the same construction; for example the construction shown in Fig. 3.
  • a unique system of weighting factor is associated with each of the integrator circuits. This means that a group of weighting factors ⁇ a(i, 1), a(i, 2), ... a(i, N) ⁇ associated with the integrator circuit 700(i) is unequal to the group of the weighting factors (a(m, 1), a(m, 2) ... a(m, N)) associated with the integrator circuit 700(m), if m*1.
  • These weighting factors are furthermore chosen such, that:
  • the non-linear networks 711 (i) are each preferably in the form of a sort of amplitude filter circuit, the relationship between its input signal d(n) and its output signal b(i; n) being mathematically described by the expressions:
  • the quantity sign ⁇ d(n) ⁇ represents the polarity of d(n).
  • Fig. 8 shows a transmitter and Fig. 9 a receiver for a DPCM-transmission system using prediction circuits 7 which are assembled in a way which satisfies the general implementation shown in Fig. 7.
  • For the transmitter shown in Fig. 8 it then holds that
  • For the receiver shown in Fig. 9 it then holds that:

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)
  • Transmitters (AREA)
  • Train Traffic Observation, Control, And Security (AREA)
  • Amplifiers (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Claims (2)

1. Système de transmission à modulation par impulsions codées différentielles (DPCM) comprenant un émetteur et un récepteur, dans lequel:
A. l'émetteur comprend:
a.1. des moyens (1, 2, 3) pour produire un signal d'information à transmettre,
a.2. un dispositif de codage DPCM (4) comprenant:
aa.1. un producteur de différence (5) auquel le signal d'information à transmettre est appliqué par l'intermédiaire d'une première entrée et un premier signal de prédiction par l'intermédiaire d'une seconde entrée pour produire un signal de différence;
aa.2. un dispositif quantificateur (6) auquel le signal de différence est appliqué et qui produit un signal de différence quantifié;
aa.3. un premier circuit de prédiction (7) pour produire le premier signal de prédiction et comportant une entrée à laquelle le signal de différence quantifié est appliqué ainsi qu'une sortie couplée à la seconde entrée .du producteur de différence;
a.3. un circuit de codage à canal (8) pour convertir le signal de différence quantifié en un signal de canal numérique;
B. le récepteur comprend:
b.1. un circuit décodeur de canal (9) pour convertir les signaux de canaux numériques reçus en un signal de canal décodé;
b.2. un dispositif de décodage DPCM (10) comprenant:
bb.1. un dispositif sommateur (11) auquel le signal de canal décodé est appliqué par l'intermédiaire d'une première entrée et un second signal de prédiction par l'intermédiaire d'une seconde entrée;
bb.2. un second circuit de prédiction (7) pour produire le second signal de prédiction et comportant une entrée à laquelle le signal de canal décodé est appliqué et comportant aussi une sortie couplée à la seconde entrée du dispositif sommateur,
b.3. des moyens (12, 13, 14, 15) pour traiter le signal de somme produit par le dispositif sommateur, caractérisé en ce que le premier et le second circuit de prédiction (7) comprennent chacun deux ou plus de deux canaux de prédiction congruents (710(1); 710(2)) constitués chacun d'un réseau non linéaire (711(1); 711(2)), présentant une fonction de transfert non linéaire, suivi d'un circuit intégrateur à fuite (700(1); 700(2)), l'entrée de chaque réseau non linéaire (711 (1 ), 711 (2)) étant connectée à l'entrée (701 )du circuit de prédiction (7), les circuits intégrateurs (700(1); 700(2)) étant tous de la même construction, un jeu particulier de facteurs de pondération étant associé à chaque circuit intégrateur, la sortie de ces circuits intégrateurs étant connectée aux entrées d'un dispositif additionneur (712) dont la sortie est connectée à la sortie (702) du circuit de prédiction.
2. Système de transmission suivant la revendication 1, pour lequel, pour le canal de prédiction ayant le numéro i, la relation entre le signal d'entrée d(n) du réseau non linéaire (711(i)), et son signal de sortie b(i; n) est donnée par l'expression:
Figure imgb0015
où A(i) représente une constante positive avec A(0)=0 et A(i+1)>A(i) et sign (d(n)} représente la polarité de d(n).
EP82201438A 1981-11-17 1982-11-15 Système de transmission à modulation par impulsions codées différentielles Expired EP0079658B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82201438T ATE22514T1 (de) 1981-11-17 1982-11-15 Differenzpulskodemodulationsuebertragungssystem.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8105196 1981-11-17
NL8105196A NL8105196A (nl) 1981-11-17 1981-11-17 Differentieel pulscode modulatie overdrachtstelsel.

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EP0079658A1 EP0079658A1 (fr) 1983-05-25
EP0079658B1 true EP0079658B1 (fr) 1986-09-24

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US (1) US4481644A (fr)
EP (1) EP0079658B1 (fr)
JP (1) JPS58125928A (fr)
AT (1) ATE22514T1 (fr)
AU (1) AU552686B2 (fr)
CA (1) CA1193734A (fr)
DE (1) DE3273485D1 (fr)
NL (1) NL8105196A (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8203950A (nl) * 1982-10-13 1984-05-01 Philips Nv Differentieel pulscodemodulatie overdrachtstelsel.
AU570439B2 (en) * 1983-03-28 1988-03-17 Compression Labs, Inc. A combined intraframe and interframe transform coding system
AU572556B2 (en) * 1983-10-07 1988-05-12 Dolby Laboratories Licensing Corporation A/d encoder and decoder
NL8303567A (nl) * 1983-10-17 1985-05-17 Philips Nv Inrichting voor het weergeven van videosignalen.
GB2189106B (en) * 1986-04-14 1990-02-14 Philips Electronic Associated Image display

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3354267A (en) * 1965-01-13 1967-11-21 Bell Telephone Labor Inc Differential pcm system employing digital integration
CA1085044A (fr) * 1975-04-03 1980-09-02 Yukihiko Iijima Systeme de communication code a prevision avec reaction composite pour signal de television en couleur incluant une porteuse de chrominance
JPS5550738A (en) * 1978-10-05 1980-04-12 Nec Corp Decoding method of adaptability forecasting type differential pulse code and its unit
FR2445660A1 (fr) * 1978-12-28 1980-07-25 Pissard Andre Procede et circuit de transmission de type mic differentiel a prediction adaptive, utilisant un filtrage par sous-bandes et une analyse spectrale
US4255763A (en) * 1979-12-26 1981-03-10 Bell Telephone Laboratories, Incorporated Technique for reducing transmission error propagation in an adaptively predicted DPCM video encoder

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CA1193734A (fr) 1985-09-17
AU9047882A (en) 1983-05-26
EP0079658A1 (fr) 1983-05-25
US4481644A (en) 1984-11-06
ATE22514T1 (de) 1986-10-15
AU552686B2 (en) 1986-06-12
NL8105196A (nl) 1983-06-16
JPH0245855B2 (fr) 1990-10-12
JPS58125928A (ja) 1983-07-27
DE3273485D1 (en) 1986-10-30

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